Global greenhouse gas emissions will rise by 52% by 2030, unless the world takes action to reduce energy consumption, a study has warned.

The prediction comes from the latest annual World Energy Outlook report from the International Energy Agency (IEA).

It says that under current consumption trends, energy demand will also rise by more than 50% over the next 25 years.

The IEA adds that oil prices will "substantially" rise unless there is extra investment in oil facilities.

It says the world has seen "years of under-investment" in both oil production and the refinery sector.

The organisation estimates that the global oil industry now needs to invest $20.3 trillion (£12 trillion) in fresh facilities by 2030, or else the wider global economy could suffer.

'Unsustainable'

"These projected trends have important implications and lead to a future that is not sustainable," said IEA chief Claude Mandil.

If investments [in oil fields] do not come in a timely and sufficient manner, there will be higher oil prices, and global economic growth will suffer

IEA chief economist Fatih Birol

"We must change these outcomes and get the planet onto a sustainable energy path."

The IEA's warning comes at a time when the Kyoto climate change agreement calls on developed nations to cut their greenhouse gas emissions to 5% below 1990 levels by 2008-12.

It also cautions that oil producers need to double annual investments in their oil fields or else see another £13 a barrel on the projected price of oil over the next 25 years.

Economic impact

The IEA says this extra investment is vital to avoid the supply bottlenecks that saw oil prices rise above $70 a barrel in late August.

"If investments do not come in a timely and sufficient manner, there will be higher oil prices, and global economic growth will suffer," said IEA chief economist Fatih Birol.

The IEA says the world has enough oil supplies to last until 2030, and that the core issue is instead the need to improve the supply chain.

Greenpeace said the latest figures from the IEA showed just how important it was for countries to meet their Kyoto targets.

"The Kyoto protocol doesn't amount to much in terms of emissions reductions but at least it breaks the curve [of rising emissions] among countries that have accepted its targets," said Steve Sawyer, climate policy expert at the environmental pressure group.

"We have to work out the trick of how to get the US and the rapidly industrialising developing countries to break the curve as well."

The IEA is made up of the 26 main industrialised nations who are the major oil consumers.